Here is an excerpt from the specification:
Returns an array of strings naming the files and directories in the directory denoted by this abstract pathname.
If this abstract pathname does not denote a directory, then this method returns null. Otherwise an array of strings is returned, one for each file or directory in the directory. Names denoting the directory itself and the directory's parent directory are not included in the result. Each string is a file name rather than a complete path.
Because "searchThis" does not exists so it is returning null and "files" object is being re initialized to null.